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Diuretic and Natriuretic Actions of Melanin Concentrating Hormone in Conscious Sheep
Author(s) -
Parkes David G.
Publication year - 1996
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1996.tb00686.x
Subject(s) - medicine , endocrinology , hematocrit , vasopressin , chemistry , melanin concentrating hormone , aldosterone , hormone , urine osmolality , antidiuretic , neuropeptide , receptor
Melanin concentrating hormone (MCH) is a 19 amino‐acid peptide expressed in high concentrations within the dorso‐lateral hypothalamus of rats, sheep and man. MCH regulates skin colour and ACTH release in teleost fish, however, its physiological relevance in mammals is unclear. The present study examined the cardiovascular and metabolic actions of intracerebroventricular (i.e.v.) infusion of MCH, and the pro‐MCH derived peptide Neuropeptide‐E‐I (NEI), in conscious, chronically instrumented sheep. Human MCH (1–19) or NEI (1–13) was infused i.e.v. for 24 h into 6 sheep, and measurements were made every 10 min of arterial pressure, heart rate, cardiac output, stroke volume and peripheral blood flow/conductance. Recordings of water intake (H 2 Oin), urine volume (Uv), urinary Na (UNaV) and K excretion (UKV) were made, as well as hematocrit, plasma Na, K, osmolality, protein, glucose, ACTH, vasopressin, renin, endothelin, ANF, Cortisol and aldosterone concentrations. After 24 h of infusion at 10 μg/h, MCH produced a significant increase in Uv from 0.8 ± 0.2 to 1.4 ± 0.3 l/day, together with an increase in UNaV from 56 ± 8 to 107 ± 14 mmol/day, and in UKV from 202 ± 18 to 369 ± 38 mmol/day. H 2 Oin was unchanged. Similar renal changes were observed during i.e.v. infusion of NEI. There was no change in any cardiovascular parameter, although hematocrit showed a large decrease with infusion of both peptides after 24 h infusion. Plasma osmolality increased from 291 ±1 to 295 ± 1 mOsm/kg during MCH infusion, whereas total protein and plasma Na and K were unchanged. MCH increased plasma glucose from 3.4 ± 0.2 to 3.8 ± 0.2 mmol/l. Plasma aldosterone exhibited a 30–40% decrease following MCH or NEI infusion, whereas all other plasma concentrations remained unchanged. This study has shown that i.c.v. infusion of MCH or NEI can produce diuretic, natriuretic and kaliuretic changes in conscious sheep, triggered by a possible increase in plasma volume as indicated by the changes in hematocrit. These results, together with anatomical data reporting the presence of MCH/NEI in fluid regulatory areas of the brain, indicate that MCH/NEI may be an important peptide involved in the central control of fluid homeostasis in mammals.